[PATCH] D67151: [SystemZ] Recognize INLINEASM_BR in backend

[Ulrich Weigand via Phabricator via llvm-commits]

uweigand added inline comments.


================
Comment at: lib/Target/SystemZ/SystemZInstrInfo.cpp:1550
+  case SystemZ::INLINEASM_BR:
+    return SystemZII::Branch(SystemZII::AsmGoto, 0, 0, nullptr);
+
----------------
Please add a comment why we're not registering any branch targets.


================
Comment at: lib/Target/SystemZ/SystemZInstrInfo.h:128
+
+  bool isRelative() { return Target != nullptr && Target->isReg(); }
+  bool hasMBBTarget() { return Target != nullptr && Target->isMBB(); }
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The name seems weird.  If the branch target is a register operand, we have an **indirect** branch, not a relative branch.  (In fact, relative branches are those that have an MBB target operand!)

As I'm not sure there's anything we can ever do to optimize an indirect branch, I'm not sure why we even need this.


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Comment at: lib/Target/SystemZ/SystemZMachineScheduler.cpp:112
+                        (TII->getBranchInfo(*I).isRelative() ||
+                         TII->getBranchInfo(*I).getMBBTarget() == MBB));
     HazardRec->emitInstruction(&*I, TakenBranch);
----------------
Aha, here's the user.  But I don't understand it -- what is supposed to be testing?  Why would we want to handle indirect branches here?


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  https://reviews.llvm.org/D67151/new/

https://reviews.llvm.org/D67151